Plastic (polymeric resin) is often the material of choice for components in electronic products such as computers, photocopiers, and the like because it offers design flexibility, cost-effective manufacturing, and light weight products. In order to function efficiently in such applications, normally insulating polymeric resin must be made electrically conductive to provide electromagnetic shielding, electrostatic dissipation or antistatic properties to such components.
Polymeric resins are typically made conductive by incorporating electrically conductive fillers such as carbon fibers, metal powders or flakes, vapor grown carbon fibers, carbon nanotubes, carbon black, and the like. However, the incorporation of carbon fibers having diameters greater than about 3 micrometers is detrimental to other properties such as the impact and surface finish of the composite. Metal powders and flakes greatly increase the specific gravity of polymeric compositions, making them less cost effective, while the use of carbon black can lead to components that exhibit sloughing. In recent years vapor grown carbon fibers (VGCF) and carbon nanotubes having diameters less than 75 nanometers have been found to maintain electrical conductivity while minimizing those problems associated with other conductive fillers. However the high cost of VGCF/carbon nanotubes makes the development of improved, cheaper, conductive polymeric composites important.
An improved, conductive, polymeric composition comprises a polymeric resin; and an electrically conductive filler system comprising small carbon fibers and carbon powder, fibrous non-conductive filler or a combination of carbon powder and fibrous non-conductive filler. The amount of the electrically conductive filler system utilized is dependent upon the desired electrical conductivity (surface and volume conductivity or resistivity) while preferably preserving intrinsic properties of the polymeric resin such as impact, flex modulus, class A finish, and the like. The conductive articles made from these compositions can therefore be used for electromagnetic shielding, electrostatic dissipation or antistatic purposes in packaging, electronic components, housings for electronic components and automotive housings.